This invention relates broadly to the art of Foley-type urethral drainage catheters, and more particularly to safety mechanisms for use with such catheters.
Voluntary control over discharge of bladder contents is a serious and distressing problem for persons whose natural anatomy is no longer capable of completely controlling the outflow of urine from the bladder for such reasons as advanced age, surgery, disease, trauma, denervation, and other malformation of the natural lower urinary tract.
A traditional urethral balloon catheter of a well-known type comprises a flexible catheter tube which extends from outside the body along the urethra and into the bladder. The catheter tube comprises a main lumen for passage of urine and a much smaller lumen leading to an annular expandable balloon, which is adjacent the distal end of the catheter and which can be expanded within the bladder by pumping a fluid along the smaller lumen to thereby prevent accidental retraction of the catheter from the urethra. Typically in such a system, urine continuously drains through the catheter main lumen which is, in turn, connected to a length of drainage tubing and finally a drainage bag worn by, or at least maintained near, the patient.
Although urethral catheters of the type described above are quite beneficial and solve many problems, they also create other problems. For example, such a catheter main lumen which extends from outside the body into the body provides a path along which, if one is not careful, bacteria can enter, or invade, the body. For this reason, it is common for urethral catheter systems to be constructed and used as "closed systems". That is, it is desirable that the flexible, internal, catheter-drainage tubes have sealed connections with the exterior drainage tubes leading to the bags worn by the patients so that they cannot be easily separated (which would allow bacteria to invade the lumen and migrate into the body). Thus, it is an object of this invention to provide a normally "closed system" indwelling urethral catheter system.
Yet another problem which is encountered with indwelling urethral catheters is that externally extending tubes thereof can accidentally snag on surrounding objects. Similarly, agitated, demented, disoriented, and/or otherwise confused patients can pull on externally extending tubes voluntarily. Such stresses on the external tube are transmitted to the internal tubes and balloons and can be disastrous for such patients, especially if extirpation (defined as the forceful and traumatic withdrawal of a Foley-type urinary catheter through the urethra while the bladder-retaining balloon is still inflated) ensues which can cause frank hematuria, urethral lacerations, stricture formation, infections, prostatitis, impotence, etc. For example, if a patient wearing such an indwelling urethral catheter system were being "wheeled" through the hospital on a heavy hospital bed and the external tubing should catch on a stationary structure, axial tension would be exerted along the tube to the balloon which is located in the patient's bladder. The balloon, now held taut against the bladder neck and sphincter, exerts a resistance, or stress, on the tube which, under a continual load, causes the tube to stretch. Since a standard catheter tube is relatively elastic, it will stretch to almost one and one half times its normal length before it begins to exert a deforming force on the balloon. Eventually,-however, the balloon will deform getting thinner at its connection to the tube, and when sufficient force is applied, it will be pulled out of the bladder and along the urethra, typically causing lacerations or ruptures of the urethra and/or sphincter muscle. If the balloon is of such a size or this force too great, the catheter tube may break. When this occurs, the distal portion of the catheter next to the balloon is retained inside the patient's bladder. It is then necessary to use a cystoscope to remove those portions of the balloon catheter system remaining in the patient's body.
The incidence of extirpation varies widely. It is more common in extended-care facilities, for wheelchair-bound patients, and increases where the care-giver's skill level decreases. The level of occurrence would have to be classified as unusual, but not rare, since nearly every health-care provider has personally witnessed and/or treated this problem. When extirpation occurs, factors which will affect the degree of damage caused thereby are the amount of fluid in the balloon, the balloon size, the type of catheter material (latex versus silicon), the force applied to the catheter (a gentle continuous force normally is less damaging than a rapidly applied force), and pre-existing anatomic conditions of the patients (enlarged prostate, spastic bladder, scarring, radiation, etc.). Normally, latex balloons tend to more easily deform than silicone balloons and therefore cause less damage than do the more rigid silicone balloons.
When the catheter tube is first stretched, as described above, the patient feels discomfort and therefore usually realizes that there is a problem and takes action to solve the problem. However, this is not always possible. Thus, it is an object of this invention to provide a urethral catheter system which has a safety mechanism for protecting the patient from undue tension placed on external tubes of urethral catheter systems.
Catheter-drainage tubes of prior art urethral catheter systems normally contain a forked external section, with one branch of the fork defining the main drainage lumen and the other branch of the fork (the inflation pigtail) defining the balloon-inflating lumen of the balloon. The branch defining the main lumen normally includes, integral and as one part therewith, an enlarged female terminal funnel portion for receiving a male connector of an external bag-drainage tube. The male connector of the bag-drainage tube has a long tapered external surface which mates in a tight-press fit with a relatively long internal surface of the enlarged female terminal funnel portion. This press fit contains a large surface area of contact to ensure that the connection remains sealed against bacterial invasion and that these members do not easily separate. To further ensure that there is no leakage or separation commercially available systems commonly tape this connector junction. If the catheter bag/system is purchased as separate components, nurses quite frequently place tape at the connecting edges between the elongated female terminal funnel portion of the catheter-drainage tube and the male connector of the bag-drainage tube. However, this not only prevents bacteria migration and ensures that there is no separation, but it also ensures that, should the external tubing become snagged, an undue amount of axial force will be applied to the balloon which can cause severe injury to the patient, as mentioned above.
Thus, it is another object of this invention to provide a connection between a catheter-drainage tube and a bag-drainage tube which ensures that there is no leakage or separation under normal circumstances, but which, in a calibrated manner, does allow separation if an excessive axial force is applied to external tubes of a urethral catheter "closed system."
Yet another problem, related to those already discussed for urethral catheter systems, is that if there is a separation between the bag-drainage tube and the catheter-drainage tube, or if either of these two tubes breaks, not only will bacteria be allowed to invade the system, and therefore enter the patient, but also foul-smelling and possibly contaminated urine will be released which is unsanitary to surroundings, disagreeable and potentially dangerous to workers, and highly embarrassing to the patient. Thus, it is another object of this invention to provide a urethral catheter system which automatically separates in a calibrated manner upon the application of an excessive axial force above a particular threshold tension thereto, but which, when it does separate, prevents escape of fluid and migration of bacteria.
It is yet another object of this invention to provide a urethral catheter system which not only protects the patient and surroundings, as mentioned above, but which is also not unduly expensive.